Field of the Invention
The present disclosure relates to the technical field of display, and in particular, to a pixel unit, a method of manufacturing the same and a display device.
Description of the Related Art
A basic structure of an Organic Light-Emitting Diode (OLED) device is of a sandwich-like structure formed by connecting a thin and transparent layer of Indium Tin Oxide (ITO) to an anode of a power supply and providing a metal cathode, wherein the ITO layer has semiconductor characteristics. The whole structure comprises a hole transmission layer (HTL), a light-emitting layer (EL) and an electron transmission layer (ETL). When the power supply supplies a suitable voltage, holes of the anode and charges of the cathode will combine with each other in the light-emitting layer to generate light. Light with three primary colors, i.e., red color, green color and blue color (RGB), can be generated according to different recipes thereof to form basic colors.
Generally, external quantum efficiency of an OLED depends on internal quantum efficiency thereof and light extraction efficiency. At present, light extraction efficiency of the OLED device is mainly restricted by the following two factors:                1. Total reflection of the light at an electrode-air interface and a glass-air interface will restrict light extraction, because difference in refractive index between different medium materials is great; such difference in refractive index causes only light rays emitted from a light-emitting point source within a certain range of angle to exit, and thus no matter how many times the light out of this certain range of angle is reflected, it cannot escape out of the device to form exiting light, thereby being absorbed by the material inside the device finally;        2. The light reflected by the respective interfaces forms a waveguide mode in the medium material and is absorbed by the material through conduction.        
FIG. 1 shows a schematic structural view of a cross-section of an OLED unit in the prior art. As shown in FIG. 1, the OLED unit comprises an anode layer 1, a pixel definition layer 2, an organic light-emitting layer 3 and a cathode layer 4. The anode layer 1 includes a plurality of pixel anodes in an array arrangement. The pixel definition layer 2 covers the anode layer 1, but does not cover the part of each pixel anode which will be used as a light-emitting region. The organic light-emitting layer 3 is located within the light-emitting region, and the cathode layer is disposed on the organic light-emitting layer 3. From the formed structure, it can be seen that spaces between the respective portions of the organic light-emitting layer 3 within the respective light-emitting regions are fully filled with the pixel definition layer 2. Furthermore, since the area of the pixel anode is substantially equal to that of the light-emitting region, the light L emitted from a side of the organic light-emitting layer 3 runs through a longer light path inside the pixel definition layer 2, and a part of the light L directly enters into a bottom glass substrate after passing through the pixel definition layer 2 and then is absorbed, such that this part of the light L cannot exit out of a display screen.